Neuroscience: The Biological
Perspective
Chapter 2
Chapter 2 Menu
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How parts of nervous system relate
Neurons and nerves and how they work
How neurons communicate
Neurotransmitters
How brain and spinal cord interact
Somatic nervous system; interacting with surroundings
Autonomic nervous system and reaction to stress
Study of the brain and how it works
Structures and functions of the bottom part of the brain
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Structures that control emotion, learning, memory, motivation
• Parts of cortex controlling senses and movement
• Parts of cortex responsible for higher forms of thought
• Differences between left side and right side of the brain
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Hormones interact with nervous system and affect behavior
Parts of nervous system
Overview of Nervous System
• Nervous System - an extensive network
of specialized cells that carry
information to and from all parts of the
body.
• Neuroscience – deals with the structure
and function of neurons, nerves, and
nervous tissue.
• Relationship to behavior and learning.
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Neurons and nerves
Structure of the Neuron
• Neurons - the basic cell that makes up
the nervous system and which
receives and sends messages within
that system.
• Parts of a Neuron
• Dendrites - branch-like structures that
receive messages from other neurons.
• Soma - the cell body of the neuron,
responsible for maintaining the life of the
cell.
• Axon - long tube-like structure that carries
the neural message to other cells.
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Neurons and nerves
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Neurons and nerves
Other Types of Brain Cells
• Glial cells - grey fatty cells that:
• provide support for the neurons to grow on
and around,
• deliver nutrients to neurons,
• produce myelin to coat axons,
• Myelin - fatty substances produced by certain
glial cells that coat the axons of neurons to
insulate, protect, and speed up the neural
impulse.
• clean up waste products and dead
neurons.
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Neurons and nerves
Neurons in the Body
• Nerves – bundles of axons in the body
that travel together through the body.
• Neurilemma – Schwann’s membrane.
• Tunnel through which damaged nerve fibers
can repair themselves.
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Neurons and nerves
Generating the Message:
Neural Impulse
• Ions – charged particles.
• Inside neuron – negatively charged.
• Outside neuron – positively charged.
• Resting potential - the state of the neuron when not
firing a neural impulse.
• Action potential - the release of the neural impulse
consisting of a reversal of the electrical charge within
the axon.
• Allows positive sodium ions to enter the cell.
• All-or-none - referring to the fact that a neuron either
fires completely or does not fire at all.
• Return to resting potential.
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LO 2.2
Neurons and nerves
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Sending the Message to Other Cells
• Axon terminals - branches at the end of the axon.
• Synaptic knob – rounded areas on the end of axon
terminals.
• Synaptic vesicles - sack-like structures found inside the
synaptic knob containing chemicals.
• Neurotransmitters - chemical found in the synaptic vesicles
which, when released, has an effect on the next cell.
• Synapse/synaptic gap - microscopic fluid-filled space
between the rounded areas on the end of the axon
terminals of one cell and the dendrites or surface of
the next cell.
• Receptor sites - holes in the surface of the dendrites
or certain cells of the muscles and glands, which are
shaped to fit only certain neurotransmitters.
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Neuron communication
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Neuron Communication
• Neurons must be turned ON and OFF.
• Excitatory neurotransmitter - neurotransmitter that
causes the receiving cell to fire.
• Inhibitory neurotransmitter - neurotransmitter that
causes the receiving cell to stop firing.
• Chemical substances can affect neuronal
communication.
• Agonists - mimic or enhance the effects of a
neurotransmitter on the receptor sites of the next
cell, increasing or decreasing the activity of that
cell.
• Antagonists - block or reduce a cell’s response to
the action of other chemicals or neurotransmitters.
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Neurotransmitters
• Types of neurotransmitters
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Neurotransmitters
Cleaning up the Synapse
• Reuptake - process by which
neurotransmitters are taken back into
the synaptic vesicles.
• Enzyme - a complex protein that is
manufactured by cells.
• One type specifically breaks up
acetylcholine because muscle activity
needs to happen rapidly, so reuptake
would be too slow.
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Brain and spinal cord
Central Nervous System
• Central nervous system (CNS) - part of
the nervous system consisting of the
brain and spinal cord.
• Spinal cord - a long bundle of neurons that
carries messages to and from the body to
the brain that is responsible for very fast,
lifesaving reflexes.
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The Reflex Arc: Three Types of Neurons
• Sensory neuron - a neuron that carries information
from the senses to the central nervous system.
• Also called afferent neuron.
• Motor neuron - a neuron that carries messages from
the central nervous system to the muscles of the
body.
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Also called efferent neuron.
• Interneuron - a neuron found in the center of the
spinal cord that receives information from the sensory
neurons and sends commands to the muscles
through the motor neurons.
• Interneurons also make up the bulk of the neurons in the
brain.
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Brain and spinal cord
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Somatic nervous system ----- Autonomic nervous system
Peripheral Nervous System
• Peripheral nervous system (PNS) - all
nerves and neurons that are not
contained in the brain and spinal cord
but that run through the body itself;
divided into the:
• Somatic nervous system
• Autonomic nervous system
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Somatic nervous system
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Somatic Nervous System
• Soma = body.
• Somatic nervous system - division of the
PNS consisting of nerves that carry
information from the senses to the CNS and
from the CNS to the voluntary muscles of the
body.
• Sensory pathway - nerves coming from the
sensory organs to the CNS consisting of sensory
neurons.
• Motor pathway - nerves coming from the CNS to
the voluntary muscles, consisting of motor
neurons.
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Autonomic Nervous System
• Autonomic nervous system (ANS) - division of
the PNS consisting of nerves that control all
of the involuntary muscles, organs, and
glands sensory pathway nerves coming from
the sensory organs to the CNS consisting of
sensory neurons.
• Sympathetic division (fight-or-flight system) - part
of the ANS that is responsible for reacting to
stressful events and bodily arousal.
• Parasympathetic division - part of the ANS that
restores the body to normal functioning after
arousal and is responsible for the day-to-day
functioning of the organs and glands.
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Peeking Inside the Brain
• Clinical studies
• Deep lesioning - insertion of a thin, insulated
wire into the brain through which an electrical
current is sent that destroys the brain cells at
the tip of the wire.
• Electrical stimulation of the brain (ESB) –
milder electrical current that causes neurons
to react as if they had received a message.
• Human brain damage.
• Electroencephalograph (EEG) machine designed to record the brain
wave patterns produced by electrical
activity of the surface of the brain.
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Peeking Inside the Brain
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Computed tomography (CT) - brain-imaging
method using computer controlled X-rays of the
brain.
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Magnetic resonance imaging (MRI) - brain-imaging
method using radio waves and magnetic fields of the
body to produce detailed images of the brain.
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Functional MRI (fMRI) – computer makes a sort of
“movie” of changes in the activity of the brain using
images from different time periods.
Positron emission tomography (PET) - brainimaging method in which a radioactive sugar is
injected into the subject and a computer compiles
a color-coded image of the activity of the brain
with lighter colors indicating more activity.
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Structures of the bottom part of brain
The Brain Stem
• Medulla - the first large swelling at the top of
the spinal cord, forming the lowest part of
the brain, which is responsible for lifesustaining functions such as breathing,
swallowing, and heart rate.
• Pons - the larger swelling above the medulla
that connects the top of the brain to the
bottom and that plays a part in sleep,
dreaming, left–right body coordination, and
arousal.
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Structures of the bottom part of brain
The Brain Stem
• Reticular formation (RF) - an
area of neurons running
through the middle of the
medulla and the pons and
slightly beyond that is
responsible for selective
attention.
• Cerebellum - part of the lower
brain located behind the pons
that controls and coordinates
involuntary, rapid, fine motor
movement.
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Structures of the bottom part of brain
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Structures controlling emotion, learning, memory, and motivation
Structures Under the Cortex
• Limbic system - a group of several brain
structures located under the cortex and
involved in learning, emotion, memory, and
motivation.
• Thalamus - part of the limbic system located in the
center of the brain, this structure relays sensory
information from the lower part of the brain to the
proper areas of the cortex and processes some
sensory information before sending it to its proper
area.
• Olfactory bulbs - two projections just under the
front of the brain that receive information from the
receptors in the nose located just below.
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Structures controlling emotion, learning, memory, and motivation
Structures Under the Cortex
• Limbic system (continued)
• Hypothalamus - small structure in the brain
located below the thalamus and directly above the
pituitary gland, responsible for motivational
behavior such as sleep, hunger, thirst, and sex.
• Sits above and controls the pituitary gland (master
endocrine gland).
• Hippocampus - curved structure located within
each temporal lobe, responsible for the formation
of long-term memories and the storage of
memory for location of objects.
• Amygdala - brain structure located near the
hippocampus, responsible for fear responses and
memory of fear.
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Structures controlling emotion, learning, memory, and motivation
Cortex
• Cortex - outermost covering of the brain
consisting of densely packed neurons,
responsible for higher thought
processes and interpretation of sensory
input.
• Corticalization – wrinkling of the cortex.
• Allows a much larger area of cortical cells
to exist in the small space inside the skull.
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Structures controlling emotion, learning, memory, and motivation
Human cortex compared to various animal species
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Parts of cortex controlling senses and movement
Cerebral Hemispheres
• Cerebral hemispheres - the two sections of the cortex
on the left and right sides of the brain.
• Corpus callosum - thick band of neurons that
connects the right and left cerebral hemispheres.
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Parts of cortex controlling senses and movement
Four Lobes of the Brain
• Occipital lobe - section of the brain located at the rear
and bottom of each cerebral hemisphere containing
the visual centers of the brain.
• Primary visual cortex – processes visual
information from the eyes.
• Visual association cortex – identifies and makes
sense of visual information.
• Parietal lobes - sections of the brain located at the top
and back of each cerebral hemisphere containing the
centers for touch, taste, and temperature sensations.
• Somatosensory cortex - area of neurons running
down the front of the parietal lobes responsible for
processing information from the skin and internal
body receptors for touch, temperature, body
position, and possibly taste.
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Parts of cortex controlling senses and movement
Four Lobes of the Brain
• Temporal lobes - areas of the cortex located just behind
the temples containing the neurons responsible for the
sense of hearing and meaningful speech.
• Primary auditory cortex – processes auditory
information from the ears.
• Auditory association cortex – identifies and makes
sense of auditory information.
• Frontal lobes - areas of the cortex located in the
front and top of the brain, responsible for higher
mental processes and decision making as well
as the production of fluent speech.
• Motor cortex - section of the frontal lobe located at the
back, responsible for sending motor commands to the
muscles of the somatic nervous system.
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The homunculus is commonly used today in
scientific disciplines, such as psychology, as a
teaching or memory tool to describe the distorted
scale model of a human drawn or sculpted to
reflect the relative space human body parts
occupy on the somatosensory cortex (sensory
homunculus) and the motor cortex (motor
homunculus).
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Parts of cortex responsible for higher thought
Association Areas of Cortex
• Association areas - areas within each lobe of the cortex
responsible for the coordination and interpretation of
information, as well as higher mental processing.
• Broca’s aphasia - condition resulting from damage to Broca’s
area (usually in left frontal lobe), causing the affected person to
be unable to speak fluently, to mispronounce words, and to
speak haltingly.
• Wernicke’s aphasia - condition resulting from damage to
Wernicke’s area (usually in left temporal lobe), causing the
affected person to be unable to understand or produce
meaningful language.
• Spatial neglect - condition produced by damage to the
association areas of the right hemisphere resulting in an inability
to recognize objects or body parts in the left visual field.
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Parts of cortex responsible for higher thought
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Parts of cortex responsible for higher thought
Spatial neglect
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Left side and right side of brain
Split Brain Research
• Cerebrum - the upper part of the brain
consisting of the two hemispheres and
the structures that connect them.
• Split brain research
• Study of patients with severed corpus
callosum.
• Involves sending messages to only one
side of the brain.
• Demonstrates right and left brain
specialization.
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Left side and right side of brain
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Left side and right side of brain
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Left side and right side of brain
Split-brain subjects stared at a dot and viewed a composite of two faces (A). When asked
what they saw, subjects chose the child—the image sent to the verbal left hemisphere (B).
But when subjects pointed to the face with the left hand, they chose the woman with
glasses—whose image was received by the right hemisphere (C) (Levy et al., 1983).
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Left side and right side of brain
Language is primarily a left hemisphere activity for most individuals
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Left side and right side of brain
Results of Split Brain Research
• Left side of the brain:
• seems to control language, writing, logical
thought, analysis, and mathematical abilities,
• processes information sequentially,
• can speak.
• Right side of the brain
• controls emotional expression, spatial perception,
recognition of faces, patterns, melodies, and
emotions,
• processes information globally,
• cannot speak.
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Hormones and nervous system
The Endocrine Glands
• Endocrine glands - glands that secrete chemicals
called hormones directly into the bloodstream.
• Hormones - chemicals released into the bloodstream by
endocrine glands.
• Pituitary gland - gland located in the brain that
secretes human growth hormone and influences all
other hormone-secreting glands (also known as the
master gland).
• Pineal gland - endocrine gland located near the base
of the cerebrum that secretes melatonin.
• Thyroid gland - endocrine gland found in the neck
that regulates metabolism.
• Pancreas - endocrine gland that controls the levels of
sugar in the blood.
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Hormones and nervous system
The Endocrine Glands
• Gonads - the sex glands that secrete
hormones that regulate sexual development
and behavior as well as reproduction.
• Ovaries - the female gonads.
• Testes - the male gonads.
• Adrenal glands - endocrine glands located on
top of each kidney that secrete over 30
different hormones to deal with stress,
regulate salt intake, and provide a secondary
source of sex hormones affecting the sexual
changes that occur during adolescence.
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Hormones and nervous system
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Chapter 2 Power Point: The Biological Perspective